Busway switch



Sept. 11, 1962 Filed Sept. 24, 1958 L. M. HARTON ETAL BUSWAY SWITCH 5 Sheets-Sheet 1 INVENTORfi LYNN M HARTON, WAYNE LRHENDERsQM BYWM/QLCWJ7 Se t. 11, 1962 L. M. HARTON ETAL 3,053,945

BUSWAY SWITCH Filed Sept. 24, 1958 s Sheets-Sheet 2 INVENTORS' LYNN M. HARTON, WAYNE LR. HENDERSON L. M. HARTON ET AL Sept. 11, 1962 BUSWAY SWITCH 5 Sheets-Sheet 3 Filed Sept. 24, 1958 JIL m ,m T W M mm R ML NE Y A W P 1962 M. HARTON ETAL 3,053,945

BUSWAY SWITCH Filed Sept. 24, 1958 5 Sheets-Sheet 5 INVENTORS LYNN M. HARTQN, WAYNE LR. HENDERSON A TTOR/VEY ite States ()ur invention relates to electric switches and particularly to electric switches of relatively large capacity, adapted for use with electric power busways, i.e., electric power distribution systems of the bus bar type.

Patent application Serial Number 763,056, Fisher, filed September 24, 1958, and assigned to the same assignee as the present invention, discloses a busway switch of the type referred to which includes two sets of aligned side-by-side bus bars, the two sets having mutually overlapping contact end portions. A plurality or set of movable bridging contact members is arranged to be moved simultaneously into and out of bridging engagement between corresponding pairs of such bus bar contact portions, and means is included for applying clamping pressure transversely of the assembly when the movable contacts are in contact closed position. The movable contact members are, moreover, moved vertically, i.e., in a direction perpendicular to the general direction of the bus bars.

In operating busway switches constructed in accordance with the aforementioned Fisher application, difriculties are encountered, especially in larger sizes involving a large number of bus bars, when moving the contacts vertically into or out of engagement between the corresponding stationary contact surfaces. For example, distortion of the bus bars in the portion thereof adjacent the contact areas sometimes occurs because of the friction involved. Such friction results largely from the fact that, in a switch of this type, it is not possible to maintain adequate clearance between the contact end portions of the bus bars to permit the unimpeded entrance of the bridging contact members. This, in turn, is due to the fact that, in an assembly of this type including a large number of bars, substantial transverse movement of some of the bus bar ends is required in order to clamp the contact portions together. Thus, for example, an assembly may be considered comprising twelve bus bars having end portions overlapping the corresponding end portions of a second set of twelve bus bars, and provided with a given clearance between the overlapped end portions for the entrance of contact members. According to the prior construction, clamping pressure is applied from one side of the contact assembly, clamping all the bus bar contact portions and contact bridging members against each other, toward the opposite side of the switch enclosure. It will be observed that the bus bar end farthest away from the aforesaid side of the enclosure must travel a distance substantially equal to twelve times the original clearance provided between each overlapped pair of contact portions and its corresponding movable contact element. Each contact portion of the bus bars is, moreover, movable only by virtue of the flexing of the bus bar portion between it and the nearest insulating support. The distance which such bus bar end can travel practically is, therefore, very limited, firstly, because no matter what clearance is originally provided, the bus bar will, after the assembly has once or twice been clamped up into compressed condition, return only so far as its inherent resilience will cause it to move, this distance being relatively small as will be appreciated since the bus bars are preferably constructed of high electrical conductivity grade copper or aluminum. Secondly, such transverse travel of the bus bar ends is restricted because it is desirable for purposes of simplification that no "ice mechanism be required to positively move such bus bar end portions back to an original position beyond the amount determined by the aforesaid resilience of the bus bar portions. The existence of relatively high friction has, in the prior design, greatly restricted the manual operation of the device, even when force-reducing gearing is provided. It will be readily appreciated that when larger capacity switches are desired, such, for instance, as including 33 bus bars, the problems relating to friction alignment, and distortion, mentioned in connection with the prior design, are greatly magnified.

-It is an object of the invention to provide a busway switch which may be operated even in large sizes without requiring excessive force and without distortion of its conductors.

-It is another object of the invention to provide a busway switch which is rugged in construction and dependable in operation.

It is an object of the present invention to provide a busway switch which is comparatively small and compact.

Additional specific objects and advantages of the invention will in part become obvious and in part be pointed out in the following detailed description.

In accordance with the present invention, an improved busway switch, is provided including an enclosure containing two sets of side-by-side bus bars having end portions exposed and in interleaved transversely aligned relation generally centrally of the housing for interconnection by bridging contact elements. Means are provided, carried by the housing, for applying clamping pressure between each of the opposite sides of the housing and the centrally located assembly of overlapped bus bar ends and bridging contact elements so that clamping pressure is applied simultaneously from the two opposite sides inwardly toward the center of the enclosure.

In accordance with another aspect of the invention, the movable bridging contact elements are movable along a longitudinal path parallel to the bus bars to avoid the exertion of any forces on the bus bar ends transverse to their general direction.

In accordance with still another aspect of the invention, the busway switch is adapted for use in combination with a primary circuit disconnecting device such as a circuit breaker, and interlocking auxiliary miniature switches are provided in the busway switch and operated thereby to prevent the maintaining of the circuit in closed condition by the primary device when and if the busway switch is in one of a plurality of predetermined conditions.

In the drawings:

FIGURE 1 is a perspective view of a busway switch incorporating the present invention, an end portion thereof being broken away;

FIGURE 2 is a top plan view of the busway switch of FIGURE 1, end portions thereof being broken away;

FIGURE 3 is a sectional view taken on the line 33 of FIGURE 2;

FIGURE 4 is a sectional view taken on the line 44 of FIGURE 2;

FIGURE 5 is a sectional view taken on the line 55 of FIGURE 2;

FIGURE 6 is a perspective view of a movable contact assembly utilized in the busway switch of FIGURE 1;

FIGURE-S 7 and 8 are enlarged plan views of the contact portions of the switch of FIGURE 1 with the movable contacts shown in the OE and on positions respectively;

FIGURE 9 is an enlarged elevation view in section showing particularly the clamping mechanism utilized in the busway switch of FIGURE 1;

FIGURES 10-14 are semi-schematic diagrams showing the busway switch of FIGURE 1 used in conjunction with a conventional circuit breaker, and showing the interconnection of the interlocking switches.

'In FIGURE 1 the invention is shown as incorporated in a busway switch having a generally rectangular main enclosure portion which is mounted upon a specially constructed bus duct section comprising opposed side rail members 12 and 13, which extend continuously through the central enclosure 10 and which have attached thereto top and bottom cover plate sections 14 and 15, and having supported therein two sets 16 and 17 of side-by-side elongated parallel bus bar conductors supported therein by conventional insulating supporting means, not shown, such, for example, as shown in Patent No. 2,468,614, E. T. Carlson, assigned to the same assignee as the present invention. The bus bars of each of the sets 16 and 17 have exposed contact portions 16a and 17a overlapping each other and disposed in side-byside alignment generally centrally of the main enclosure 10 as shown particularly in FIGURES 2, 3, 7 and 8. The bus bars 16 and 17 are also provided with a suitable insulating coating 16' and 17 throughout the major intermediate portions thereof,

Referring now particularly to FIGURES 2 and 3, a pair of pan shaped or channel shaped supporting plates 19 and 20 are mounted on the side rails 12 and 13 respectively, by suitable mean such as by bolts 21. The bolts 21 also serve to mount a pair of channels 22, extending parallel to the duct portion side rails 12 and 13, which, in turn, support vertically extending channel member 23. The main supporting plates 19 and 20, and the auxiliary members 22 and 23, serve to support switch operating mechanism to be described.

The two sets of bus bars 16 and 17 are provided with interleaving overlapping contact end portions 16a and 17a, see FIGURES 7, 8 and 9. The end portions 16a and 17a are uninsulated, the insulating Wrapping 16' and 17 being discontinued short of the end of the corresponding bus bars.

For the purpose of insulating each pair of overlapped bus bars 16 and 17 from the adjacent pair of overlapped bus bars, there is provided a plurality of relatively thin insulating sheets 24. As seen in FIGURE 5, the insulating sheets 25 are generally rectangular in shape and have the corners notched at 26 to provide an interfitting engagement with the corners formed by the intersection of the enclosure of the main section 10 and the duct section covers 14 and 15. In other words, the insulating plates 25, while being located mainly in the main enclosure 10, include short projecting portions which project into the duct sections at each side of the main housing 10.

For the purpose of selectively connecting or disconnecting the bus bars 16 to and from the bus bars 17, there is provided a number of movable bridging contact elements 27. The movable contact members 27 are movable between an on position as indicated in FIGURE 8, in which each contact member 27 is wedged tightly between the overlapping exposed portions 16a and 17a of the bus bars, and an off position, as indicated in FIG- URE 7, to which they are slid longitudinally away from the aforementioned on position to break the electrical connection between the bars 16 and 17.

The movable contacts 27 are supported in insulating carrier assemblies 28 which are held in side-by-side stacked relation by suitable means such as by bolts 29. Each insulator carrier assembly 28 includes five sheets of insulating material comprising a central insulating sheet 28a and two outward insulating sheets 28b and 280 mounted on either side of the central sheet 28a. The outermost insulating sheets 28 each have an elongated opening 30 cut therein from one edge toward and stopping short of the opposite edge thereof and the inner insulating sheets 28a and 28b likewise have portions thereof cut away to provide a retaining pocket for trapping 4 the conductive slug 27 which serves as the movable contact. The entire assembly 23 moves longitudinally of the bus bar assembly to move the movable contact between oflf and on positions as previously described, the cutaway portions 36 providing clearance for the bus bars 16 and 17 respectively.

In the embodiment of the invention illustrated, an assembly of thirty-three bus bars is provided, and therefore, thirty-three insulating assembly carriers 28 must be provided for the movable contacts. For the purpose of supporting the movable insulating carriers 28 and for moving them simultaneously between on and off positions, a generally rectangular boxlike framework is provided including a pair of generally rectangular end-plates 31 and 32, which are movably supported by means of rollers 33 upon the inner surfaces of the flanges of the side rails 12 and 13, as shown particularly in FIGURES 3 and 5. The plates 31 have a generally central rectangular aperture 34- for a purpose to be described. The end-plates 31 and 32 are interconnected by four angleiron corner braces 35 which are bolted to the end-plates 31 and 32 by bolts 36. The corner braces 35 also engage the corners of the insulating assemblies 28 and retain them in position. It will be observed, therefore, that the entire assembly including all the movable contacts 27 and the insulating carriers 28, may be moved longitudinally between the off and 011 positions by means of the framework including the end-plates 31 and 32 and the corner braces 35 the assembly rolling along the inner surfaces of the flanges of the side rails 12 and 13 on rollers 33.

For the purpose of moving the movable contact assembly between the off and on positions, manually operable operating mechanism is provided as illustrated particularly in FIGURES 4 and 5.

In accordance with this aspect of the invention, the end-plates 31 and 32 are each provided with gear racks 37 and 38 fixedly attached to the end-plates 31 and 32 by means of bolts 39. In addition, two transversely extending driving rods and 41 are provided having driving or pinion gears 42 and 43 adapted to engage and drive the racks 37 and 38 respectively, at each side of the assembly.

For the purposes of facilitating the manual operation of the rods 49 in order to move the contact assemblies as described, force-reducing mechanism is provided as shown handle 52 causes the worm gears 47 and 48 to drive the gears 49 and 50 turning the rods 46 and 41, the gears 42 and 43 driving the racks 37 and 38 to move the movable contact assembly.

In order to establish good electrical conductivity be tween the bars 16 and 17 in the closed position of the switch, it is necessary that an extremely high amount of force, in the neighborhood of 2000 pounds, be applied to each overlapping joint. In accordance with the present invention, this large force is readily provided by manually operable means to be described. For this purpose, and referring particularly to FIGURE 9 of the drawings, a transversely extending rod or shaft 54 is provided, extending between the end-plates 19 and 20 and journalled thereon in suitable bearings 55 and 56. Adjacent the bearings 55 and 56, the rod 54 is provided with gears 57 connected by means of link drive chains 58 to driven gears 59 and 69. The gears 59 and 60 include hub portions 71 and 72, and are fixedly attached to screws 61 and 62 by means of pins 71a and 72a. The screw members 61 and 62 are each provided with an axial bore or opening 61a and 62afor a purpose to be described. The tapped members 63 and 64 engaged by screw members 61 and 62 are non-circular in cross-section and are slidably retained in recesses 65 and 66 provided in pairs of retaining blocks 67 and 68. See particularly FIGURES 4 and 9. The retaining blocks 67 and 68 are bolted to the plates 19 and 20 by suitable means such as by bolts 69 and 71 respectively. Outward movement of the screw members 61 and 62 is limited by reason of the endwall of the hub portions 71, 72, riding against the flange portions 75', 76' of the bearings 75, 76 carried by channel members 22 respectively.

For the purpose of applying transverse clamping pressure to the stacked assembly of insulating plates 25, bus bar ends 16a and 17a and movable contact members 27, there is provided a pair of pressure members 78 and 79 of disc shape having stem or rod extensions 80 and 81 fixedly attached thereto by suitable means such as by welding and extending into the bores or axial openings of the screw members 61 and 62. In order to provide resilient energy storing means, an assembly of conical spring members 82 is provided, carried by the stem portions 80 and 81 of the pressure members 78 and '79 respectively. The conical springs 82 are preferably arranged in seriesparalle relation, that is, they are arranged in nested groups with the convex sides of the springs of each adjacent group facing in opposite directions. The screw members 61 and 62 have oppositely directed threads, that is, one is provided with a right-hand thread and the other provided with a left-hand thread. In operation, rotation of the shaft 54 such as by means of the handle member 33 is transmitted by means of the drive chains 58 to the gear members 59 and 60, causing simultaneous rotation of the screw members 61 and 62. In one direction of rotation, the screw members 61 and 62 tend to move outwardly of the tapped members 63 and 64. Since the screw members 61 and 62 are rigidly attached to the hub members 71 and 72, which in turn bear against the flange portions of the bearing members 75 and 76, outward movement of these screw members is, of course, not possible. As a result, such rotation of the screw members 61 and 62 moves the tapped blocks 63 and 64 inwardly, toward each other. This inward movement of the tapped blocks 63 and 64 is transmitted to the conical spring members 82 through the washers 84 and 85 and from the conical spring members to the assembly of overlapped bus bar contact portions through the pressure members 78 and 79, thereby securely clamping together all of the overlapped end portions. Rotation of the shaft 54- in the opposite direction, of course, moves the tapped blocks 63 and 64 in an outwardly direction, allowing the conical spring members 82 assembly to expand and, thereby relieving the pressure on the overlapped bus bar contact portions.

It will be observed that since the channel members 22 are securely bolted to the plates 19 and 20, as mentioned above and as shown particularly in FIGURE 3 a very high amount of pressure may be applied to the overlapped bus bar end portions. It will also be further understood that the plate members 19 and 20 are securely and rigidly connected together by means such as transversely extending tie rods 86 seated in transversely extending insulating channel members 87 and bolted to the housing side rails 12 and 13 by means of nuts 88.

The sequence of operation of the busway switch is, therefore, as follows:

Assuming the switch to be in the off or open circuit position such as shown, for instance, in FIGURE 5 and in FIGURE 7, the handle 52 is first rotated to move the assembly of movable contact members 27 to the closed circuit position, as indicated in FIGURE 8 and in dotted lines in FIGURE 5, by means of the transport mechanism described above. Following this, the handle 83 is rotated to apply clamping pressure upon the transversely aligned assembly of overlapped bus bar ends and movable contact members 16a, 17a and 27. The switch is then in the 6 fully closed position, and exhibits electrical current carrying capacity equal to or slightly greater than that of a continuous busway run of the same number of bars.

It will be observed that when the shaft 54 is rotated by means of the handle 83, both the pressure members 84 and are urged inwardly toward the bus bar assembly simultaneously, with substantially equal pressure being applied from opposite sides. Because of this, the entire assembly of overlapped bus bar ends when clamped together occupies a position substantially central of the housing 10 both before and after clamping. Thus, the central bars of the assembly are not required to deflect any substantial amount between the clamped and unclamped conditions, and the outermost bars are required to deflect a distance equal to approximately /2 the distance that such corresponding bars would have to deflect if the pressure were exerted from one side only.

While the busway switch of the present invention may be used to interrupt currents of low or moderate amplitude, the primary function of the switch is to electrically isolate a portion of a busway or power circuit from a power source associated therewith, after the source has been electrically de-energized by means of a high current capacity switch or circuit breaker connected in series therewith. It is, therefore, important that the busway switch of this type should not be operated from the closed toward the open position when currents of high magnitude are flowing therethrough. Conversely, it is extremely desirable that in going from a circuit open to a circuit closed position, the main power controlling device, such as a circuit breaker, should not be closed until and unless the busway switch is completely closed with fully adequate pressure applied to the contacts.

For the purpose of providing an indication of the presence or absence of adequate contact pressure, the busway switch is provided with a miniature push-button-operated auxiliary control switch 89, see FIGURES 2 and 3, fixedly mounted with respect to the main enclosure by suitable means such as by being bolted to a supporting bracket 90 mounted in fixed relation to the plate member 20. There is, furthermore, provided a movable stop member 91 having an adjustable projection comprising bolt 92 and being threadedly engaged with a threaded portion of the shaft 54. The member 91, moreover, is prevented from rotating by means of its sliding engagement with the angle guide member plate 93 carried by a wall of the enclosure 10. See FIGURE 5. The member 91 also carries an indicator plate 94 which extends to the right as viewed and has a portion 94' disposed to be visible through an aperture 10a in the enclosure 10. See FIG- URE 1. Thus, a visible indication is provided of the pressure condition of the switch. In operation, as the shaft 54 is rotated to apply pressure to the overlapped bus bar ends as described above, the member 91 travels along the threaded portion of the shaft 54 to the right as viewed in FIGURES 2. and 3. When the shaft 54 has been rotated the desired number of turns to apply the desired amount of clamping pressure, the projection 92 engages the operating member of the switch 89 and operates it.

In FIGURE 10 there is illustrated schematically an arrangement in which a plurality of busway switches 10 constructed in accordance with the present invention are used in conjunction with a primary circuit protecting device comprising a conventional circuit breaker 98 including a manually operable handle member 99 and an automatic operating mechanism including a trip member 100 which is movable to cause automatic opening of the circuit breaker mechanism. The circuit breaker 98 further includes a solenoid 101 including a plunger which is movable when the solenoid 161 is energized to strike the trip member 100 and cause automatic operation of the circuit breaker 98. The circuit breaker 93, therefore, constitutes a primary circuit disconnecting and load interrupting device which may be remotely operated by electrical means. It will be appreciated, of course, that other types of remotely electrically operable load interrupting devices may be used. The busway switches it) are connected in parallel relation with the output of the circuit breaker 98 and are used to control the power provided for respective loads 1 and 2. When used in an application such as illustrated in FIGURE 10, it is desirable for safety reasons that each busway switch 10 shall not be operated in any manner to change it from a given position to another given position while the circuit breaker 98 is in the closed circuit condition. Thus, it should not be possible to commence movement of the movable contacts of the switch it} from open position toward closed position, while the circuit breaker 93 is in closed circuit position. Conversely, it should not be possible to close the circuit breaker 98 so as to deliver power to the loads 1 or 2 unless each busway switch is either in its fully opened condition, or in its fully closed position with full pressure applied. For the purpose of providing these various interlocking functions, three auxiliary miniature switches having pushbutton type actuators are employed, comprising the aforementioned pressure switch $9, a full open travel switch tea, and a full closed travel switch 103. The pressure switch 39 is best shown in FIGURES 2 and 3, and the open and closed travel switches 102 and 1%, respectively, are best shown in FIGURE 5.

The open and closed travel switches i182 and 1635, respectively, are rigidly mounted on the housing of the main enclosure portion it by suitable means such as by screws 1M. For the purpose of actuating the switches 102 and 103 respectively, the end-plate 31 is provided with adjustable actuating members comprising bolts 1G5 and 196 threadedly engaged in supporting brackets 107 and 1&8, respectively, rigidly mounted on the end-plate 31. The bracket MS has an extension 103' (see FIG- URE disposed to be visible through an aperture (not shown) in the enclosure 19. Thus, a visible indication is provided of the contact position of the switch.

Each of the limit switches 89, 182 and 103 comprises two pairs of stationary contacts and a movable bridging actuator adapted to move between two positions in each of which it bridges a respective pair of said stationary contacts, and is spring biased toward a normal position in which it closes a particular set of contacts. The switch circuit is shown schematically in FIGURE 11 for each busway switch 10. As shown in FIGURE 11, indicating lamps 1&9, 11d and 111 are connected in series with each pair of normally open contacts of each of the switches 89, 192 and 1%, respectively, for the purpose of providing a visual indication of the actuated condition of the corresponding switch. As shown in FIGURE 11, when the switch is in its fully open position such as shown in FIGURE 5, the switch 192 is actuated interrupting continuity of the circuit between the terminals AA, therefore permitting the circuit breaker 98 to be actuated or closed. Upon movement of the contact carrier assembly of the switch toward circuit closed position, the actuator of the switch 102 is released and is closed by its bias spring, thereby establishing continuity of the circuit between the terminals AA and causing actuation of the solenoid 101 to hold the breaker 98 in its tripped condition. When the carrier 31 reaches its fully closed position as indicated in dotted lines in FIG- URE 5, the switch 103 is actuated as indicated in FIG URE 13. It will be observed, however, that the circuit between the terminals AA is still complete through the limit switch 559. When the full contact pressure has been applied to the busway switch by means of handle 83, the switch 89 is actuated, thereby interrupting the circuit between the terminals A A as indicated in FIGURE 14 and permitting operation of the circuit breaker It will be observed that it is necessary that the contact carrier be in its fully closed position and that full pressure be applied before resetting and closing of the circuit breaker 98 is possible, Thus, even though full pressure may be applied to the contact end portions of the bus bars 16 and 1'7, if the carrier is not in its fully closed position, the circuit breaker will remain tripped. It will be further observed that because of the parallel arrangement of the outputs AA of each of the busway switches 16, the existence of a predetermined condition in any one of said switches will cause actuation of the circuit breaker 98 regardless of the conditions existing in the other busway switches, and this is accomplished with the use of only a single solenoid 101 in the circuit breaker 98.

While there has been shown in detail only one specific embodiment of the invention, it will be readily apparent that many modifications thereof may be made by those skilled in the art. It is therefore intended by the appended claims to cover all sueu modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric switch comprising an enclosure, at least two sets of side-by-side bus bars supported in substantially end-to-end alignment in said enclosure, said sets of bus bars having exposed overlapping and interleaving contact portions disposed in transverse alignment generally centrally of said enclosure, a plurality of relatively movable contacts movable between a first position in which they bridge a corresponding pair of contact portions of said bus bars and a second position remote from said first position, means for effecting movement of said movable contacts between said first and second positions, and means for applying clamping pressure to the overlapped assembly of bus bar contact portions and said movable contacts when in contact-closed position, comprising a pair of pressure members each movable with respect to said enclosure and mounted at substantially opposite points at each side of said assembly and in alignment with said overlapped contact portions, and means for forcing said pressure members in respectively opposite directions simultaneously.

2. An electric switch comprising a housing, at least two sets of elongated parallel bus bars supported in substantial endwise alignment in said housing, said sets of bus bars having exposed end contact portions extending in overlapped spaced-apart relation in a single row within said housing, at least one set of movable contact members, means for moving said movable contact members between an on position in which each of said movable contact members is positioned between a corresponding pair of contact portions of said bus bars and an off position removed from said on position, and means for applying contact pressure to said overlapped bus bar contact portions transversely of said housing comprising a pair of first pressure members rotatably supported in aligned bearings at opposite ends of said row of contact portions, a pair of slidable pressure members supported in said housing substantially coaxial with said first pressure members, said first pressure members and said slidable pressure members having cam-acting interengaging portions to cause oppositely-directed simultaneous transverse movement of said slidable pressure members by rotational movement of said first pressure members, and resilient means between said slidable pressure members and said overlapped assembly of bus bar contact portions to transmit forces from said pressure members to said contact portions.

3. An electric switch comprising an enclosure, a plurality of pairs of side-by-side aligned contact portions supported in a single row in said enclosure, means for compressing all of said contact portions together transversely of said enclosure comprising a pressure transmitting plate member on each end of said row of contact portions and each including an integral elongated guide portion extending away from said contact portions, resilient force transmitting means carried by each said guide portion respectively, a pair of relatively separable pressure-applying members for each of said guide portions and each including an axial bore or opening therein through which a portion of said guide portion extends, means supporting one of each pair of said separable members for sliding movement parallel to said row of contact portions, bearing means stationary with respect to said enclosure for supporting the other one of each pair of said separable members for rotation on an axis extending parallel to said row of contact portions, and interengaging cam means carried by said separable members respectively to cause relative movement of said relatively separable pressure-applying members in opposite directions, said bearing means including thrust bearing portions engaging said rotatable pressure-applying members and limiting axial movement thereof.

4. An electric power busway switch comprising a main housing of generally rectangular configuration, a pair of longitudinally extending housing end portions of generally rectangular cross-section extending from said main housing, a set of elongated closely-spaced parallel bus bars supported in side-by-side alignment in each of said housing end portions, said sets of bus bars having overlapping contact portions extending into closely-spaced overlapped relation generally central of said main housing, a plurality of relatively stationary sheets of relatively thin insulating material disposed in said main housing between adjacent pairs of said overlapped bus bar contact portions, an assembly of relatively movable contact members, each of said contact members being carried by a generally rectangular carrier plate of insulating material, all of said insulating carrier plates being supported for movement in unison longitudinally of said hous ing end portions and parallel to said bus bars between a first position in which said movable contact members are respectively between corresponding pairs of bus bar contact portions, and a second position removed from said first position, means for moving said assembly of movable contact members comprising a pair of gear rack assemblies mounted on said movable contact assembly at each side thereof, and a pair of pinion gears supported for rotation in said housing and arranged to drive said rack gears respectively longitudinally of said housing end portions, and means for operating said pinion gears simultaneously from a point externally of said housing.

5. An electric switch as set forth in claim 4 wherein said switch also includes a force transmitting shaft rotatably supported and extending transversely of said assembly of contact members, a pair of screw-type clamping means carried by said housing on opposite sides of said contact assembly for forcing said contact members and contact portions into firm mutual engagement, and means connecting said transversely extending rod to each of said clamping means, respectively, for operation of said clamping means simultaneously from outside said enclosure.

6. An electric power busway switch comprising a main enclosure, a plurality of aligned side-by-side spaced pairs of contact members, a set of relatively movable contact members, means for moving said movable contact members in unison between on and oil positions, means for applying contact pressure transversely of the assembly of contact members when said movable contact members are in said on position, a first limit switch arranged to be operated when said movable contact members are in said on position, a second limit switch arranged to be operated when said movable contact members are in said off position, and a third limit switch arranged to be operated when said contact pressure-applying means is in its maximum pressure position, means for operating said pressure-applying means externally of said housing, means for operating said contact member moving means externally of said housing, and means for making electrical connection to all of said limit switches from outside said housing.

7. An electric busway switch comprising: an enclosure having opposite end portions for connection in a busway system; a first set of elongated parallel bus conductors extending from one end portion of said enclosure to a central portion thereof; a second set of elongated parallel bus conductors extending from the other end portion of said enclosure to the central portion thereof in overlapping interleaving relationship with said first set of bus conductors, the overlapping portions of both sets of said bus conductors having uninsulated cooperating contact portions spaced apart in a single row within said enclosure; a plurality of bridging contact members for making electrical contact between respective pairs of said overlapping contact portions; means supporting said bridging contact members for movement parallel to the length of said bus conductors from a first position between respective pairs of overlapping contact portions to a second position removed from said contact portions and between the respective bus conductors of one set of bus conductors; and means for applying transverse clamping force to the overlapped contact portions of said bus conductors when said contact members are in said first position between respective contact portions comprising a pair of movable pressure members, one of said pressure members being positioned on each end of said row of overlapping contact portions within said enclosure to 'bear against respectively endmost ones of said bus conductors, and an operating mechanism linking both of said pressure members for forcing said pressure members simultaneously in respectively opposite directions inward toward the center of said row of contact portions.

8. An electric busway switch comprising: an enclosure having opposite end portions for connection in a busway system; a first set of elongated parallel bus conductors extending from one end portion of said enclosure to a central portion thereof; a second set of elongated parallel bus conductors extending from the other end portion of said enclosure to the central portion thereof in overlapping interleaving relationship with said first set of bus conductors, the overlapping portions of both sets of said bus conductors having uninsulated cooperating contact portions spaced apart in a single row within said enclosure; a plurality of bridging contact members for making electrical contact between respective pairs of said overlapping contact portions; means supporting said bridging contact members for movement from a first position between respective pairs of overlapping contact portions to a second position removed from said contact portions; and means for applying transverse clamping force to the overlapped contact portions of said bus conductors when said contact members are in said first position between respective contact portions comprising a pair of movable pressure members, one of said pressure members being positioned on each end of said row of overlapping contact portions within said enclosure to bear against respectively endmost ones of said bus conductors, and an operating mechanism linking both of said pressure members for forcing said pressure simultaneously in respectively opposite direction inward and toward the center of said row of cont-act portions.

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